The invention relates to a clutch disc for a motor vehicle friction clutch and particularly a clutch disc the friction lining carrier of which is coupled rotationally elastically with a hub of the clutch disc both through a spring system dimensioned for the transmission of an under-load torque and through a spring system dimensioned for the transmission of an idling torque.
Such a clutch disc is known for example from German Patent No. 1,801,969. The friction lining carrier of this clutch disc is rotationally elastically connected with the hub through a torsional vibration damper dimensioned for operation under load. This under-load vibration damper comprises coupling springs which are seated in windows of a hub disc protruding radially from the hub, and side discs arranged axially on both sides of the hub disc. The side discs are connected with the friction lining carrier so that the coupling springs are resiliently stressed on rotation of the side discs in relation to the hub disc. A friction device damps the torsional vibrations.
The hub of the clutch disc comprises an inner hub for coupling with the input shaft of the motor vehicle gearing and an outer hub carrying the hub disc. The outer hub is provided with an internal toothing in which an external toothing of the inner hub engages with play in rotation. In pockets of the external toothing of the inner hub there are seated coupling springs dimensioned for the transmission of the idling torque, which are supported on the internal toothing of the outer hub and damp the torsional vibrations occurring in idling operation, by reason of the inherent friction of the hubs or of an additional friction device.
In the known clutch disc the coupling springs of the two spring systems are seated with slight initial stress in the windows of the side discs or the pockets of the hub respectively. In this way a jump occurs in the spring characteristic of the spring systems in the transition from idling operation to under-load operation, causing clutch noises and gear noises in the operation of the vehicle in the lower torque range in driving at low load.
It is the problem of the invention to improve a clutch disc of the above-explained kind so that such noises are largely suppressed or prevented with low constructional expense.